Intensive physiological analysis of the energetic metabolism of D. melanogaster with postponed aging is proposed. Previous work has shown that a number of characters involved in energetic metabolism are altered in flies with genetically postponed aging: resistance to starvation, metabolic rate, locomotor activity, flight duration, output of eggs, and so on. The proposed research would examine more D. melanogaster populations, including populations that have undergone selection on some of these characters specifically. For example, it would study the energetic metabolism of stocks selected for increased starvation resistance. In this manner, physiological genetic connections between characters can be uncovered, such as the connection between starvation resistance and reserve substances, lipid or glycogen; the latter should be increased in the stocks selected for starvation resistance if they supply the calories that increase starvation resistance. In addition, a broader range of physiological characters would be examined: age-specific metabolic rate, feeding rate, age-specific lipid and glycogen levels, in vitro uptake of lipid and glycogen by ovaries and gut, response to dietary restriction, and response to celibacy. Once this research has been completed, it will be apparent which tissues and which catabolic enzymes would be of greatest interest for further research on the physiology of postponed aging. In addition, a number of hypotheses concerning the overall role of energetic metabolism in the evolution and physiology of aging, such as the hypothesis of a cost of reproduction and the hypothesis that dietary restriction acts via reduction in reproductive effort, would be tested definitively, at least for D. melanogaster.